1. Field of the Invention
The present invention relates generally to a torque wrench, and more particularly to a collapsible torque wrench.
2. Description of the Related Art
A conventional torque wrench generally has torque setting function. In the case that the wrenching torque applied by the wrench to a threaded member exceeds the set value, a warning effect is created to warn a user to stop wrenching.
FIGS. 1 to 3 show a conventional torque wrench 10. The torque wrench 10 includes a shank 12. A drive head 14 is disposed at a front end of the shank 12 for connecting with a socket or fitting onto a threaded member. A rear end of the shank 12 is a pivoted end 13. A branch bar 15 is disposed on one side of the shank 12. The torque wrench 10 further includes a connection rod 16. A front end of the connection rod 16 is pivotally connected with the pivoted end 13 of the shank 12 via a pivot pin 161. The torque wrench 10 further includes a housing including a tubular body 171 and a casing 18 fixedly disposed on one side of the tubular body. The connection rod 16 is fitted in the tubular body 17. A stop member 20 is mounted in the casing 18. A front end of the stop member 20 is pivotally connected with the branch bar 15 via a pivot pin 201, whereby the stop member 20 is angularly displaceable. The body of the stop member 20 is formed with an arched locating slot 21. A rivet 22 is riveted on the casing 18 and positioned in the locating slot 21 of the stop member 20. The torque wrench 10 further includes a torque adjustment mechanism 24 mounted in the tubular body 17. The torque adjustment mechanism 24 includes a hollow fixing block 25, an elastic member 26 and an adjustment member 28. A slender rod section 162 of the connection rod 16 extends through the fixing block 25. The fixing block 25 is fixed in the tubular body 17 without possibility of move. The adjustment member 28 is screwed with the rear end of the slender rod section 162 of the connection rod 16 and partially protrudes from the rear end of the tubular body 17. The elastic member 26 is mounted in the tubular body 17. Two ends of the elastic member 26 respectively abut against the fixing block 25 and the adjustment member 28.
The necessary torque of the wrench is resettable by means of rotating the adjustment member 28. In use, a user can hold the handle 29 to rotate the wrench 10 in a direction of arrow F, whereby the drive head 14 can wrench a threaded member. In operation, the stop member 20 is angularly displaced. At this time, the housing (including the tubular body 17 and the casing 18) will slide toward the rear end of the connection rod 16 and the fixing block 25 is displaced along with the tubular body 17 to compress the elastic member 26. When the force applied by the wrench reaches the set torque, the housing and the relevant components (including the connection rod 16 and the stop member 20) will swing to one side of the wrench around the pivot pins 161, 201 and the rivet 22 is moved to the other end of the locating slot 21 of the stop member 20. In appearance, the shank 12 is bent from the housing to make the user realize that the applied force has reached the set value and stop wrenching.
It is found that the above torque wrench 10 has some shortcomings in structure and needs to be improved. These shortcomings exist because of the manner in which the fixing block 25 is fixed. In the conventional structure, the tubular body 17 is pressed with multiple recessed stripes 171 for fixing the fixing block 25. According to such fixing manner, the fixing block 25 is likely to deform. In the case of deformation of the fixing block 25, the frictional force between the fixing block and the slender rod section 162 of the connection rod 16 will increase. This will affect the smoothness of operation of the mechanism and deteriorate the precision of the torque value of the wrench.
Moreover, according to the above fixing manner of the conventional structure, it is impossible to separate the fixing block 25 from the tubular body 17 and reassemble the two components. As a result, the component cannot be independently replaced. Incase of damage, it is necessary to replace the entire mechanism. For example, in case of damage of the fixing block 25, the damaged fixing block cannot be solely replaced and it is necessary to replace the fixing block as well as the housing. The rivet 22 for locating the stop member 20 is riveted on the casing 18 so that it is hard to detach the rivet 22 from the casing 18. Therefore, incase of damage of the fixing block 25, the housing and the stop member 20 must be also replaced along with the fixing block. This leads to waste of resource. Similarly, in case of damage of the stop member 20, the housing and the fixing block 25 must be also replaced along with the stop member 20.
Accordingly, the poor structural design of the conventional torque wrench 10 leads to higher cost for replacement of the components and deterioration of the precision of the torque value and needs to be improved.